That's precisely why one needs to differentiate between a priori propositions vs. a posteriori propositions... and also between analytic assumptions and synthetic assumptions. Combine these two dimensions, and you get a nice 2x2 :) - don't we all just love'em...
- analytic a priori
- analytic a posteriori
- synthethic a priori
- synthetic a posteriori
whoa whoa..rolling out heavy stuff. dont be going all imannuel on me brotha..just dont get into metaphysical aspects and how knowledge of synthetic a priori propositions is made possible